Injection devices are known for directly injecting into the treatment substances, such as vaccines, antibiotics or vitamins, in order to limit the mortality rate or to increase growth of the embryos. Such devices conventionally comprise an injection head including a plurality of injectors capable of injecting a substance into a plurality of eggs, the injectors being mobile vertically above a conveyor for transporting eggs to be treated, and a system for distributing a substance to be injected, for distributing dosed amounts of substance to said injectors.
For example, in U.S. Pat. No. 5,941,696, a distribution system was proposed, consisting of a peristaltic pump and of flexible tubes feeding the injectors individually. The rotor of the pump is equipped with rollers which gradually compress tubes for displacing the substance towards the injectors. This type of pump guarantees good accuracy in the delivered amounts of substance. However, flexible tubes are subject to large stresses and have to be regularly replaced. Further, this type of pump requires a bundle of tubes with significant length. For each injector, a tube actually needs to be mounted between the source of substance and the injector, passing through the pump placed at a distance from the injection head. Moreover, this type of pump is not suitable for certain kinds of vaccines, notably vaccines with living cells. Indeed the pump tends to destroy a portion of the living cells during the compression of the tubes and thereby greatly reduces the efficiency of the vaccine.
Distribution systems have also been proposed comprising an individual micropump for each injector. These systems prove to be bulky, very expensive and require significant and delicate maintenance in order to guarantee proper operation of the whole of the injectors.